Electronic properties of Fabre charge-transfer salts under various temperature and pressure conditions

Abstract

Using density functional theory, we determine parameters of tight-binding Hamiltonians for a variety of Fabre charge transfer salts, focusing, in particular, on the effects of temperature and pressure. Besides relying on previously published crystal structures, we experimentally determine two new sets of structures: (TMTTF) 2 SbF 6 at different temperatures and (TMTTF) 2 PF 6 under various hydrostatic pressures. We find that a few trends in the electronic behavior can be connected to the complex phase diagram shown by these materials. Decreasing temperature and increasing pressure cause the systems to become more two dimensional. We analyze the importance of correlations by considering an extended Hubbard model parameterized using Wannier orbital overlaps and show that while charge order is strongly activated by the intersite Coulomb interaction, the magnetic order is only weakly enhanced. Both orders are suppressed when the effective pressure is increased.

Light-Induced Current Oscillations in the Charge-Ordered State of (TMTTF)2SbF6

“…The largest dispersion appears for the paths: Γ → X which is along the stacking direction, U → Γ and Z → R containing contributions of the a-directions as well. The bandwidth for the three materials is about 350 meV for the upper as well as for the lower band, being in excellent agreement with previous studies [13,14]. For the b-direction, the bands are weakly warped and intersect the Fermi energy.…”

“…This behavior is similar to applying chemical pressure, already discussed for Figure 12. This observation is supported by calculations of Jacko et al [14] who also observed an increase of the dimensionality when the crystal structure of (TMTTF) 2 PF 6 under hydrostatic pressure was taken for the calculations. Concerning the dimerization, the corresponding gap at the X-point obviously diminishes from 110 meV at 300 K to 55 meV at 100 K, again resembling the effect of pressure as demonstrated in Figure 12.…”

“…Furthermore, we used a norm-conserving PBE GGA functional for all atom types, up to a certain level taking into account the exchange correlation as well as the spatial variation of the charge density. The room-temperature crystal structure for the calculations were taken for (TMTTF) 2 PF 6 and (TMTTF) 2 AsF 6 , while for (TMTTF) 2 SbF 6 we performed x-ray scattering from T = 300 K down to 100 K [13,14,82]; the structures were not relaxed within the calculations. Due to the stoichiometry of the organic salts, they are treated as metals.…”

“…During the last years several comprehensive investigations have been conducted on the optical [5][6][7][8][9] and transport properties [10], the lattice [11,12] and electronic structure [13][14][15] as well as on the magnetic properties [16][17][18][19][20][21]. However, not much is known about the non-linear properties at the charge-order transition taking place at T CO = 157 K and transient conduction phenomena.…”

Role of layer packing for the electronic properties of the organic superconductor(BEDT−TTF)2Ag(CF3)4(Altmeyer1, Valentí2, Jeschke3 2015Phys. Rev. BSelf Cite100100View full textAdd to dashboardCite

“…For a few decades organic charge-transfer (CT) salts built of donor and acceptor molecular complexes have attracted a lot of attention due to the variety of ground states in their phase diagrams [1][2][3][4][5] . Application of external or chemical pressure can lead to antiferromagnetic insulating, charge ordered, spin-density wave, spin liquid, or unconventional superconducting ground states.…”